<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>弹性伸缩比</title>
    <style>
        /* 默认情况下，主轴方向尺寸是靠内容撑开测轴默认拉伸 */
        .box {
            display: flex;
            /* flex-direction: column; */
            height: 300px;
            border: 1px solid #000;
        }

        .box div {
            /* height: 100px; */
            background-color: pink;
        }

        .box div:nth-child(1) {
            width: 200px;
        }
        .box div:nth-child(2){
            flex:1
        }
        .box div:nth-child(3){
            flex:2
        }
        </style>
</head>

<body>
    <div class="box">
        <div>1</div>
        <div>2</div>
        <div>3</div>
    </div>
</body>

</html>